Certain embedded defects such as shallow trench isolation (STI) voids, which may result in electric defects such as a contact-gate short have been the most critical yield detractors for advanced technology development due to narrower process windows resulting from aggressive scaling. Detection of critical electric defects by optical-based metrologies, e.g., bright field inspection (BFI), is challenging. For example, detection of such electric defects is beyond the physical limitations of optical-based metrologies in terms of resolution and/or contrast because such metrologies are often unable to produce enough signal response relative to corresponding noise. Consequently, electron beam inspection (EBI) has been the most popular in-line detection of electrical defects as well as physical defects. However, detection of a contact-gate short defect by EBI is still challenging because the scanning electron image of the potential defect is not a steady state of material response under electron beam (ebeam) exposure. In addition, different shorting defects may result in the same patch image when scanned along a certain direction, e.g., a standard scan direction. Thus, identification of the actual shorting location as well as the failure mechanism may be difficult to determine based on a single scan.
A need therefore exists for methodology and apparatus enabling separating real shorting defects from other charging artifacts, e.g., nuisance/false defects, and for identifying the exact shorting locations.